Baseboard heater



FIG. 1 is an isometric view of the baseboard heater;

FIG. 2 is a side view of a left side thereof;

FIG. 3 is a front view thereof;

FIG. 4 is a side view of a right side thereof;

FIG. 5 is a back view thereof;

FIG. 6 is a top view thereof; and,

FIG. 7 is a bottom view thereof.

The broken lines illustrate portions of the baseboard heater that form no part of the claimed design. 

The ornamental design for a baseboard heater, as shown and described. 